Semiconductor constructions

ABSTRACT

The invention includes a semiconductor construction comprising a semiconductor substrate, and a first layer comprising silicon and nitrogen over the substrate. A second layer comprising at least 50 weight% carbon is over and physically against the first layer, and a third layer consisting essentially of a photoresist system is over and physically against the second layer. The invention also includes methodology for forming the semiconductor construction.

RELATED PATENT DATA

This patent resulted from a divisional application of U.S. Pat.application Ser. No. 10/092,874, filed on Mar. 5, 2002, which is issuedas U.S. Pat. No. 6,713,404.

TECHNICAL FIELD

The invention pertains to semiconductor constructions and methods offorming semiconductor constructions. In particular aspects, theinvention pertains to semiconductor constructions in which an organicmaterial is provided between photoresist and a layer comprising siliconand nitrogen, and to methods of forming such constructions.

BACKGROUND OF THE INVENTION

Photolithography is a commonly-used method for patterning featuresduring semiconductor processing. A photosensitive material (photoresist)is formed over a mass which is ultimately to be patterned, and thephotoresist is subsequently subjected to radiation. The radiation isprovided in a pattern so that some portions of the photoresist areimpacted by the radiation while other portions of the photoresist arenot impacted by the radiation. The photoresist is then subjected todeveloping conditions which selectively remove either the impacted ornon-impacted portions. If the photoresist is a positive photoresist, theimpacted portions are selectively removed; and if the photoresist is anegative photoresist, the non-impacted portions are selectively removed.

The photoresist remaining after the development defines a patternedmask. The pattern of the mask can subsequently be transferred to theunderlying mass utilizing appropriate etching conditions to formpatterned features within the mass.

A difficulty which can be encountered during photolithographicprocessing is that the radiation utilized to pattern the photoresist(typically light) can be reflected from the underlying mass to causevarious constructive and destructive interference patterns to occur inthe light as it passes through the photoresist. This can adverselyaffect a pattern ultimately developed in the photoresist.

The problem is typically addressed by providing an antireflectivecoating immediately beneath the photoresist. Various antireflectivecoatings have been developed, with a deposited antireflective coating(DARC) being exemplary. Deposited antireflective coatings will typicallycomprise silicon and nitrogen, and can, for instance, consist of, orconsist essentially of, silicon, nitrogen and optionally, hydrogen.DARC's can alternatively comprise silicon, oxygen, and in some cases,hydrogen, and can be referred to as silicon oxynitride materials.

DARC materials can be particularly useful as antireflective coatingsduring photolithographic processing of metals, and/or insulativematerials (with an exemplary insulative material beingborophosphosilicate glass).

An exemplary photolithographic fabrication process utilizing a DARCmaterial is described with reference to FIGS. 1 and 2. Referringinitially to FIG. 1, a fragment of a semiconductor construction 10 isillustrated at a preliminary processing stage. Construction 10 comprisesa substrate 12. Substrate 12 can include, for example, a semiconductivematerial (such as, for example, monocrystalline silicon). To aid ininterpretation of the claims that follow, the terms “semiconductivesubstrate” and “semiconductor substrate” are defined to mean anyconstruction comprising semiconductive material, including, but notlimited to, bulk semiconductive materials such as a semiconductive wafer(either alone or in assemblies comprising other materials thereon), andsemiconductive material layers (either alone or in assemblies comprisingother materials). The term “substrate” refers to any supportingstructure, including, but not limited to, the semiconductive substratesdescribed above.

A mass 14 is supported by substrate 12. Mass 14 can comprise aninsulative material (such as, for example, borophosphosilicate glass)and/or various metals and/or metal compounds. Mass 14 is shown as asingle uniform layer, but it is to be understood that mass 14 cancomprise stacks of various materials.

An antireflective coating layer 16 is shown formed over mass 14. Layer16 will preferably comprise a DARC, such as, for example, siliconoxynitride.

A photoresist 18 is shown formed over and physically againstantireflective coating 16.

Radiation 20 is shown impacting various regions of photoresist 18.Radiation 20 will typically comprise light, and can, for example,predominately comprise light having a wavelength which is in the regionof from about 150 nanometers to about 250 nanometers. Regions ofphotoresist 18 impacted by radiation 20 are illustrated generally withthe label 22, and regions of the photoresist 18 which are not impactedby radiation 20 are illustrated generally with the label 24.

Photoresist 18 can comprise a chemically amplified photoresist. In suchapplication, radiation 20 will create a photogenerated catalyst(typically a strong acid) within regions 22 of the photoresist. Thephotoresist is then subjected to a post-exposure bake wherein thephotogenerated catalyst causes further reactions to alter solubility ofexposed regions 22 (and in some applications regions proximate exposedregions 22) relative to regions 24 in a developer solution. An advantageof utilizing chemically amplified photoresists is that such can increasethe sensitivity of photoresist to radiation by enabling a singleincident photon to be responsible for many chemical events.

Photoresist 18 can be referred to as a photoresist system to indicatethat the photoresist can comprise various components ultimately affectedby exposure of a portion of photoresist 18 to light. For instance, ifmaterial 18 comprises a chemically amplified photoresist system, it willtypically comprise a photoactive species which ultimately forms aphotocatalyst (typically an acid) upon exposure to light having asuitable wavelength. The photoactive species then interacts with othermaterials present in the photoresist system to alter chemical propertiesof the system. The material 18 can be referred to as consistingessentially of a photoresist system to indicate that the material 18consists essentially of components which are patterned during aphotolithographic process to form a mask. Photoresist system 18 can, inparticular applications, comprise a multilayer resist.

FIG. 2 illustrates construction 10 after a suitable post-exposure bake,and subsequent exposure to a developing solution. Photoresist 18 isillustrated as being a positive photoresist, and accordingly impactedregions 22 (FIG. 1) are selectively removed relative to non-impactedregions 24.

A problem with utilization of DARC is that such can scavengephotogenerated catalysts (such as acid) during the post-exposure bake ofphotoresist 18, and can accordingly interfere with the patterning of thephotoresist. For instance, the patterned photoresist of FIG. 2 is shownto comprise blocks 30 and 32 and such blocks are wider proximateantireflective coating 16 than at upper surfaces of the blocks. Thewidened regions at the blocks can be referred to as foot portions 34.Such foot portions are undesired.

It would be desirable to develop photolithographic processing methodswhich alleviate or prevent formation of foot portions 34.

SUMMARY OF THE INVENTION

In one aspect, the invention includes a semiconductor constructioncomprising a semiconductor substrate, and a first layer comprisingsilicon and nitrogen over the substrate. A second layer comprising atleast 50 weight % carbon is over and physically against the first layer,and a third layer consisting essentially of a photoresist system is overand physically against the second layer.

In another aspect, the invention encompasses a method of forming asemiconductor construction. A semiconductor substrate is provided, and afirst layer comprising silicon and nitrogen is formed over thesubstrate. A second layer comprising at least 50 weight % carbon isformed over the first layer, and a third layer consisting essentially ofa photoresist system is formed over and physically against the secondlayer. A first portion of the third layer is exposed to radiation whilea second portion of the third layer is not exposed to the radiation. Thethird layer is subjected to conditions which cause either the exposedfirst portion or unexposed second portion of the photoresist system torelease acid. The second layer also releases acid as the third layer isexposed to the conditions. After the third layer is subjected to theconditions, either the first or second portion is selectively removedrelative to the other of the first and second portion of the photoresistsystem.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic, cross-sectional view of a fragment of asemiconductor construction shown at a preliminary stage of a prior artprocessing method.

FIG. 2 is a view of the FIG. 1 fragment shown at a prior art processingstage subsequent to that of FIG. 1.

FIG. 3 is a diagrammatic, cross-sectional view of a fragment of asemiconductor construction shown at a preliminary stage of an exemplarymethod which can be encompassed by the present invention.

FIG. 4 is a view of the FIG. 3 fragment shown at a processing stagesubsequent to that of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In particular aspects, the invention encompasses provision of an organicmaterial (for example, a material comprising at least 50 weight % carbonand/or a material comprising carbon-hydrogen bonds) between a depositedantireflective coating layer (or any layer comprising silicon andnitrogen) and photoresist. An exemplary method illustrating aspects ofthe invention is described with reference to FIGS. 3 and 4.

Referring initially to FIG. 3, a wafer construction 50 comprises asubstrate 12 having a mass 14 thereover. Substrate 12 and mass 14 cancomprise identical constructions to those described above with referenceto the prior art of FIGS. 1 and 2.

An antireflective coating layer 16 is formed over mass 14. In particularaspects, mass 14 can comprise an insulative material, such as, forexample, borophosphosilicate glass, and antireflective coating layer 16can be physically against such insulative material. In other aspects,mass 14 can comprise a metal, such as, for example, titanium, tantalum,tungsten etc., and antireflective coating 16 can be physically againstsuch metal. In yet further aspects, mass 14 can comprise a metalcompound, such as, for example, tungsten nitride, titanium nitride,tantalum nitride, titanium silicide, etc., and antireflective coatinglayer 16 can be physically against such metal compound. Further,although mass 14 is shown as comprising a single uniform composition, itshould be understood that mass 14 can comprise various substructurestherein, with exemplary substructures being stacks of various materials.

Antireflective coating layer 16 can comprise, consist essentially of, orconsist of silicon, nitrogen and optionally, hydrogen. Alternatively,antireflective coating 16 can comprise, consist essentially of, orconsist of silicon, nitrogen, oxygen and optionally, hydrogen.Antireflective coating layer 16 can be referred to as a first layerprovided over a semiconductor substrate comprising the illustratedcomponents 12 and 14.

A layer 52 is formed over first layer 16. Layer 52 can be referred to asa second layer formed over the semiconductor substrate comprisingcomponents 12 and 14, and in the shown embodiment is formed physicallyagainst an upper surface of first layer 16. Second layer 52 ispreferably an organic material, and typically comprises at least 50weight % carbon. Layer 52 can comprise a polymer, such as, for example,an acrylic polymer, and further can comprise chemical cross-linksthroughout the polymer. Exemplary polymers include homopolymers andcopolymers comprising polyhydroxyethylmethacrylate,polymethylmethacrylate, substituted polymethylmethacrylate, andpolystyrene.

Layer 52 can be transparent to radiation which is ultimately utilized topattern a photoresist formed over layer 52, or can comprise componentswhich absorb at least some of the radiation passing through an overlyingphotoresist and to layer 52. Typically, the radiation utilized forpatterning a photoresist will have a wavelength within a region of fromabout 150 nanometers to 250 nanometers, and accordingly layer 52 cancomprise materials which absorb light wavelengths within a region offrom 150 nanometers to 250 nanometers. Suitable materials which can beincluded in layer 52 for absorbing such light are various dyes andchromophores (which can include chromophores incorporated into asuitable polymer). Exemplary chromophores can include, for example,benzene rings, anthracene, naphthalene, and coumarine.

Layer 52 can also comprise one or more materials which generate acidduring a bake of photoresist overlying material 52. Suitableacid-generating components are, for example, diazomethane, fluoroalkylsulfonate, alkyl sulfonate, and onium salts.

Layer 52 can, in particular applications, be spin-coated over layer 16.In such applications, a surfactant can be provided within material 52 toimprove a uniformity with which material 52 flows across layer 16.Particularly, the surfactant can improve a uniformity with whichmaterial 52 flows into openings (not shown) penetrating into or throughlayer 16, and can further improve a uniformity with which material 52flows over projecting features (not shown) extending from an uppersurface that material 52 is spin-coated over. Suitable surfactants caninclude, for example, alkyl sulfonium salts, and perfluoroalkylsulfonium.

Material 52 can further comprise various solvents. For instance,material 52 can be formed by having various polymeric precursors (whichcan include crosslinking materials) suspended or dissolved in a suitablesolvent, and spin coated over an upper surface of layer 16. Thepolymeric precursors can then be subjected to suitable conditions toform either a polymeric material from the precursors, or to harden theprecursors. The solvents can be removed before, during, and/or afterpolymerization of the precursors. It can be desired to remove all of thesolvents, or, it can be acceptable to leave some of the solventsremaining within layer 52 after polymerization. Suitable solvents caninclude, for example, ethyl lactate, methylamylketone,polypropyleneglycol monomethyletheracetate (PGMEA), and propyleneglycolmonomethylether (PGME), in applications in which the polymericprecursors comprise benzoyl peroxide, benzil and/or benzil derivatives,together with cross-linking materials selected from the group consistingof hexamethoxymethirol melamine and tetramethoxyglycouril. Of course,some precursors may exist in a liquid or other form which can beutilized without solvent, and in such applications the polymericprecursors can be provided neat over a surface of layer 16, andsubsequently polymerized.

A layer 18 comprising, consisting of, or consisting essentially ofphotoresist or a photoresist system is formed over second layer 52.Layer 18 can comprise either positive or negative photoresist, and canbe identical to the layer 18 described above with reference to the priorart illustrated in FIGS. 1 and 2. In particular applications, layer 18comprises a chemically amplified photoresist system.

In the shown embodiment, layer 18 is formed physically against an uppersurface of layer 52. Layer 18 can be referred to as a third layer formedover a semiconductor substrate comprising components 12 and 14.

Radiation 20 is shown passing into photoresist 18. Radiation 20 cancomprise the radiation discussed above with reference to prior art FIG.1, and accordingly can comprise light having a wavelength within a rangeof from about 150 nanometers to about 250 nanometers. The radiationimpacts regions 22 of resist 18, while other regions 24 of resist 18 arenot exposed to the radiation. Radiation 20 can be referred to aspatterned light utilized for photolithography.

In applications in which photoresist 18 comprises a chemically amplifiedresist, the construction 50 can be subjected to appropriate heating toaccomplish a post-exposure bake of construction 50. A suitabletemperature of the post-exposure bake is, for example, 90° C. to 150°C., in applications in which photoresist 18 comprises, for example,Sumitomo Chemical Co, Ltd, PAR718™, or JSR Microelectronics AR360™.

During the post-exposure bake, a photogenerated catalyst within regions22 (typically a strong acid) catalyzes reactions within photoresist 18to change chemical properties within regions 22 relative to theproperties within regions 24. Layer 52 is a barrier between photoresist18 and antireflective coating 16, and can alleviate or prevent layer 16from scavenging acid during the post-exposure bake. Further, layer 52can comprise a suitable component which releases acid, and accordinglyenhances acid-catalyzed reactions occurring within photoresist 18 duringthe post-exposure bake. It is noted that layer 52 can alternatively, oradditionally, be configured to release other catalysts besides acidwhich interact with various components of photoresist 18.

After the post-exposure bake, photoresist 18 is exposed to a suitabledeveloping solvent which selectively removes either the portions exposedto radiation 20 (and/or portions exposed to catalysts generated by theradiation); or the portions of resist 18 which have not been exposed toeither radiation or catalysts generated by the radiation. Inapplications in which resist 18 comprises PAR718™ from Sumitomo ChemicalCo, Ltd, of Osaka, Japan, a suitable developing solvent is OPD 4262™from Arch Chemicals, Inc., of Norwalk Conn., USA.

FIG. 4 illustrates construction 50 after exposure to a developingsolvent in applications in which resist 18 comprises a positivephotoresist. The developing solvent has thus removed portions 22 (FIG.3) exposed to radiation. In applications in which resist 18 comprises achemically amplified positive resist system, the solvent can also removeregions of layer 18 proximate to the regions 22 exposed to radiation ifsuch proximate regions are ultimately exposed to catalyst generated fromthe exposed regions 22.

Resist 18 is shown patterned into blocks 60 and 62, and unlike the priorart construction 10 of FIG. 2, the blocks do not have footer regions(the regions 34 of FIG. 2). Such footer regions are either reduced insize, or, in the shown preferred aspect of the invention, entirelyeliminated through utilization of barrier material 52 betweenantireflective coating 16 and photoresist 18.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A semiconductor construction, comprising: a monocrystalline siliconsubstrate; an insulative material layer over the monocrystalline siliconsubstrate; a first layer comprising silicon and nitrogen over andphysically against the insulative material layer; a second layercomprising at least 50 weight % carbon over and physically against thefirst layer; and a third layer consisting essentially of a photoresistsystem over and physically against the second layer.
 2. The constructionof claim 1 wherein the first layer comprises silicon, oxygen andnitrogen.
 3. The construction of claim 1 wherein the first layerconsists essentially of silicon oxynitride.
 4. The construction of claim1 wherein the second layer comprises carbon-hydrogen bonds.
 5. Theconstruction of claim 1 wherein the second layer comprises a surfactant.6. The construction of claim 1 wherein the second layer comprises apolymer.
 7. The construction of claim 1 wherein the second layercomprises a cross-linked polymer.
 8. The construction of claim 1 whereinthe second layer comprises an acrylic polymer.
 9. The construction ofclaim 1 where in the second layer comprises a component that absorbslight having a wavelength within a region from 150 nanometers to 250nanometers.
 10. The construction of claim 1 wherein the photoresistsystem comprises a chemically-amplified photoresist.
 11. Theconstruction of claim 1 wherein the insulative material of theinsulative material layer consists of borophosphosilicate glass.